Re: "safe mode" stops clock?!
From: johnf (john_f_at_bigREMOVEpond.net.au)
Date: 02/20/04
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Date: Fri, 20 Feb 2004 22:56:29 GMT
> Sharon F wrote:
>
<large snip>
>> I have yet to change the CMOS battery on any of my systems and some of
>> them are years old too. I have replaced batteries for others. On one
>> system, the battery was maintaining a charge when the computer was
>> left plugged in. Unplug the machine from an electrical source for any
>> length of time and
>> that sustained charge dissipated quickly and settings were lost.
>>
>
> Now that is strange, since the CMOS batteries aren't rechargeable.
>
I seem to recall that quite a few board manufacturers used a Supercap in
lieu of a CMOS battery, which maintained its charge via a little bit of
low-voltage detection circuitry.
Many home-phones use the same system to hold the stored-number memory up and
people are actually told that their phone has a battery, as it causes too
many problems trying to explain what a Supercap is - (which is simply an
extremely efficient capacitor that retains its charge for a much longer
period than a normal capacitor).
For anyone interested, you can have a look at an example on -
http://www.st.com/stonline/products/families/memories/nvram/support/nvcl_idx.htm
johnf
FWIW, terminology nowadays is really up the spout. The actual CMOS 'battery'
comes with packaging referring to it as such, when in fact it is a single
cell - not a battery. The term 'battery' only should refer to a string of
cells, e.g. a 12v (nominal) car battery consists of 6 x 2v cells.
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